The present invention relates to a device for identifying caries, plaque, bacterial infection, concretions, tartar and other fluorescent substances on teeth.
Such devices, with the aid of which it is possible to ascertain the presence of caries on teeth in a non-contacting manner, have been proposed repeatedly recently. In this connection, a tooth-tissue region that is to be investigated is irradiated withxe2x80x94in the ideal casexe2x80x94a monochromatic light source and fluorescent radiation is generated at the irradiated region in response thereto. This fluorescent radiation is subsequently evaluated, making use of the fact that the fluorescence spectrum of a carious tooth-tissue region is significantly different from the corresponding spectrum of a healthy tooth-tissue region. Thus, for example, in the red spectral range (approximately 550 to 650 nm) of a tooth that is infected by caries or plaque the intensity of fluorescence is clearly higher than in the case of a healthy tooth. By means of suitable detection and evaluation, a carious tooth-tissue region can thus be unequivocally distinguished from a healthy tooth-tissue region with the aid of a simple and non-contacting method of investigation.
Devices of this kind are described, for example, in DE 297 04 185 U1 or DE 197 09 500 C1. In the first instance they have a facility for generating the stimulating radiation, for example an HeNe-laser which generates stimulating radiation with a wavelength in the range between 600 nm and 670 nm. The stimulating radiation is coupled into a light-guide system by way of an optical system, which consists of a plurality of lenses or mirrors, and is directed through said light-guide system onto the tooth-tissue region that is to be investigated. In the case of the device described in DE 197 09 500 C1, the light-guide system consists of a light-guide that extends from the light source as far as the tip of a handpiece and provided at the end of which there is a light probe by means of which the light is coupled out and directed onto the desired region. The fluorescent radiation that results at the irradiated tooth-tissue region is coupled back into the light-guide system by way of the tip of the light probe and transmitted to a detecting device. Since the light-guide system is usually used to transmit both the stimulating radiation and the fluorescent radiation simultaneously, a beam splitter is located in the optical path between the stimulating-radiation source and the tooth-tissue region that is to be investigated in order to separate the two types of radiation from each other and to supply the fluorescent radiation to the detection means.
The elements of the optical diagnostic device previously described, in particular the means for generating the stimulating radiation and the optical system including the beam splitter for coupling the stimulating radiation into the light-guide system or for coupling the fluorescent radiation out, are of a certain size so that previously it was usual to arrange these elements in a central unit and to transmit the two types of radiation to or from the dental handpiece with the aid of a supply tube in which one or more light-guides are arranged.
It is the object of the present invention to improve the known devices for identifying caries, plaque, bacterial infection, concretions, tartar and other fluorescent substances on teeth in such a way that they can be realized in a comparatively simple and space-saving manner in terms of their structure.
This object is achieved generally in accordance with the invention by means of integration of components.
The object is achieved in accordance with one aspect of the invention by means of a device that is distinguished by the fact that a beam splitter, which is disposed in an optical path between a means for generating a stimulating radiation and a tooth-tissue region that is to be investigated, is formed by a planar rear side of a substantially hemispherical lens. This planar rear side is formed in such a way that the stimulating radiation is reflected in a direction of the tooth-tissue region that is to be investigated, whilst a fluorescent radiation, on the other hand, passes through it substantially without hindrance. Since a curved front side of the hemispherical lens simultaneously has a focusing effect, with the aid thereof it is possible to couple the stimulating radiation into a light-guide system and thereby possibly dispense with additional optical means therefor. The development of the optical diagnostic device in accordance with the invention is thus distinguished by its simple structure and the possibility connected therewith of being able to configure it with great indifference to outside influences. Thus the possibility additionally exists as well of arranging the important elements of the device not as before in a central unit that is separate from the handpiece, but directly in the handpiece itself.
The beam-splitting effect of the planar side of the hemispherical lens is preferably achieved in that the latter has a coating which reflects light at the frequencies of the stimulating radiation and lets through without hindrance light in the frequency range of the fluorescent radiation that is generated. There is preferably an optical filter adjacent to the planar side of the hemispherical lens in order to filter out in a better way those portions that are not required for the detection and assessment of the fluorescent radiation and which might possibly constitute a disturbance. A laser diode is preferably used in order to generate the stimulating radiation, since this only has very small dimensions and consequently can easily be integrated into a handpiece. Furthermore, the detection means can have a photodiode that is arranged behind the optical filter for the purpose of detecting the fluorescent radiation.
The way in which the stimulating radiation of the light source is directed onto the tooth-tissue region that is to be investigated is dependent upon the field of application of the optical diagnostic method. A plurality of possibilities for this are discussed in the following.
The device in accordance with the invention can, for example, be used in a very advantageous manner in periodontal diagnostics. For this, provided at the head end of the handpiece there is an optical probe which is inserted into the tooth pocket of a tooth that is to be investigated. At the tip of the probe the stimulating radiation is coupled out and directed onto the tooth-tissue region that is to be investigated. As previously described, the fluorescent radiation that results at the irradiated tooth-tissue region is also coupled back into the light-guide system with the aid of the optical probe and directed onto the hemispherical lens, acting as a beam splitter, and onto the means for evaluating the fluorescent radiation. As a result, the possibility exists of also being able to assess the region of a tooth stump, which is usually difficult to access and consequently difficult to investigate, with the aid of the simple, yet effective optical diagnostic method.
The probe preferably consists of a light-guiding material and in this connection has the form of a cone, a light wedge or a periodontal probe. In order to be able to obtain more detailed information on the depth of the tooth pocket, furthermore the probe can have markings or a scale on its outside. Furthermore, the tip of the probe is preferably mounted on the handpiece in a resilient manner in order to give the user the possibility of proportioning the probing force and consequently avoiding damage to the patient""s gum. The types of radiation can be transmitted from the hemispherical lens to the optical probe or in the opposite direction by means, for example, of a mirror that is arranged above the probe or a flexible light-guide that is connected to the end of the probe.
As has been explained before, an important advantage of the diagnostic device in accordance with the invention can be seen in the fact that it can be configured in an extremely compact manner in terms of its dimensions on account of the integration of the components. The possibility consequently exists of supplementing known dental handpieces for treating a tooth-tissue region by the optical diagnostic method and consequently of providing a combined diagnostic and treatment device. In this connection, previously it was merely known that laser-treatment units could be supplemented by the optical diagnostic method, since the light-guides present for the transmission of the laser-treatment radiation could also be utilized in a simple manner by the diagnostic system. Such a diagnostic and treatment device using laser radiation is described, for example, in DE 297 05 943 U1.
In accordance with the present invention, however, a dental device having a handpiece for the mechanical treatment of the tooth-tissue region is supplemented by the optical diagnostic method. This dental device can, for example, be a tartar-removing unit, as described in DE 83 22 850 U1, or a handpiece in which the treatment of the tooth-tissue region is effected by means of an abrasive treatment agent, as described, for example, in DE 197 42 701 A1. In the case of these known dental devices, the handpieces are as a rule filled up by the drive devices that are arranged in them for the treatment tips or transmission channels for treatment media or the like in such a way that previously it was not possible to integrate an optical diagnostic device therein as well without having to justify a further enlargement of the handpiece. These difficulties are now overcome by means of the device in accordance with the invention so that a very effective and versatile dental device can be formed. In the case of the tartar-removing unit or the hand instrument for treatment by means of an abrasive fluid, the light-guide that is required for the transmission of the radiation types can, for example, extend within the instrument tip or on the outside thereof. The possibility then exists of equipping the arrangement with an indicating device which directly intimates to the user whether the tooth-tissue region, to which the tip of the instrument is directed, is carious or loaded with concretions or films or not so that the user can match his treatment to the result of diagnosis. Furthermore, the possibility can also be provided for a control device to control the mechanical treatment automatically as a function of the result of diagnosis.